<template>
    <el-color-picker
        v-model='theme'
        :predefine="['#409EFF', '#1890ff', '#304156','#212121','#11a983', '#13c2c2', '#6959CD', '#f5222d', ]"
        class='theme-picker'
        popper-class='theme-picker-dropdown'
    />
</template>

<script>
import { mapGetters } from "vuex";
const version = require("element-ui/package.json").version; // element-ui version from node_modules
const ORIGINAL_THEME = "#409EFF"; // default color

export default {
    name: "ThemePicker",
    data() {
        return {
            chalk: "", // content of theme-chalk css
            theme: ""
        };
    },
    computed: {
        ...mapGetters(["themeColor"]),
        defaultTheme() {
            return this.themeColor;
        }
    },
    watch: {
        defaultTheme: {
            handler: function(val) {
                this.theme = val;
            },
            immediate: true
        },
        theme: {
            async handler(val) {
                const oldVal = this.chalk ? this.theme : ORIGINAL_THEME;
                if (typeof val !== "string") {
                    return;
                }
                const themeCluster = this.getThemeCluster(val.replace("#", ""));
                const originalCluster = this.getThemeCluster(oldVal.replace("#", ""));
                // console.log(themeCluster, originalCluster);

                const $message = this.$message({
                    message: "Compiling the theme",
                    customClass: "theme-message",
                    type: "success",
                    duration: 0,
                    iconClass: "el-icon-loading"
                });

                const getHandler = (variable, id) => {
                    return () => {
                        const originalCluster = this.getThemeCluster(ORIGINAL_THEME.replace("#", ""));
                        const newStyle = this.updateStyle(this[variable], originalCluster, themeCluster);

                        let styleTag = document.getElementById(id);
                        if (!styleTag) {
                            styleTag = document.createElement("style");
                            styleTag.setAttribute("id", id);
                            document.head.appendChild(styleTag);
                        }
                        styleTag.innerText = newStyle;
                    };
                };

                if (!this.chalk) {
                    const url = `https://unpkg.com/element-ui@${version}/lib/theme-chalk/index.css`;
                    await this.getCSSString(url, "chalk");
                }

                const chalkHandler = getHandler("chalk", "chalk-style");

                chalkHandler();

                const styles = [].slice.call(document.querySelectorAll("style"))
                    .filter(style => {
                        const text = style.innerText;
                        return new RegExp(oldVal, "i").test(text) && !/Chalk Variables/.test(text);
                    });
                styles.forEach(style => {
                    const { innerText } = style;
                    if (typeof innerText !== "string") {
                        return;
                    }
                    style.innerText = this.updateStyle(innerText, originalCluster, themeCluster);
                });

                this.$emit("change", val);

                $message.close();
            },
            immediate: true
        }
    },

    methods: {
        updateStyle(style, oldCluster, newCluster) {
            let newStyle = style;
            oldCluster.forEach((color, index) => {
                newStyle = newStyle.replace(new RegExp(color, "ig"), newCluster[index]);
            });
            return newStyle;
        },

        getCSSString(url, variable) {
            return new Promise(resolve => {
                const xhr = new XMLHttpRequest();
                xhr.onreadystatechange = () => {
                    if (xhr.readyState === 4 && xhr.status === 200) {
                        this[variable] = xhr.responseText.replace(/@font-face{[^}]+}/, "");
                        resolve();
                    }
                };
                xhr.open("GET", url);
                xhr.send();
            });
        },

        getThemeCluster(theme) {
            const tintColor = (color, tint) => {
                let red = parseInt(color.slice(0, 2), 16);
                let green = parseInt(color.slice(2, 4), 16);
                let blue = parseInt(color.slice(4, 6), 16);
                if (tint === 0) { // when primary color is in its rgb space
                    return [red, green, blue].join(",");
                }
                red += Math.round(tint * (255 - red));
                green += Math.round(tint * (255 - green));
                blue += Math.round(tint * (255 - blue));

                red = red.toString(16);
                green = green.toString(16);
                blue = blue.toString(16);

                return `#${red}${green}${blue}`;
            };

            const shadeColor = (color, shade) => {
                let red = parseInt(color.slice(0, 2), 16);
                let green = parseInt(color.slice(2, 4), 16);
                let blue = parseInt(color.slice(4, 6), 16);

                red = Math.round((1 - shade) * red);
                green = Math.round((1 - shade) * green);
                blue = Math.round((1 - shade) * blue);

                red = red.toString(16);
                green = green.toString(16);
                blue = blue.toString(16);

                return `#${red}${green}${blue}`;
            };

            const clusters = [theme];
            for (let i = 0; i <= 9; i++) {
                clusters.push(tintColor(theme, Number((i / 10).toFixed(2))));
            }
            clusters.push(shadeColor(theme, 0.1));
            return clusters;
        }
    }
};
</script>

<style lang='scss' scoped>
.theme-message,
.theme-picker-dropdown {
    z-index: 99999 !important;
}

.theme-picker .el-color-picker__trigger {
    height: 26px !important;
    width: 26px !important;
    padding: 2px;
}

.theme-picker-dropdown .el-color-dropdown__link-btn {
    display: none;
}
</style>
